The detection and identification of single-nucleotide polymorphisms (SNPs) in DNA is of central importance in genomic research for two different reasons. First, SNPs are responsible for, or at least involved in, several hundreds of inherited diseases such as Alzheimer, mucoviscidosis, phenylketonuria, and several types of breast- and colon cancer. Second, SNPs involved in the regulation of the liver function have an impact on the metabolism of drugs, which is related to the rapidly emerging field of theranostics or ‘personalized medicine’. SNPs can be characterized by hybridization-based assays such as microarrays: the massive parallelized readout is an advantage, but the method requires fluorescent labelling, optical readout, elevated reaction temperatures (˜80° C.) and elongated hybridization times of ˜16 hours. Even under these circumstances, thermal equilibrium between probe- and target DNA is not always guaranteed and the method has an ‘end-point’ character rather than providing dynamic information on molecular recognition between complementary or mismatched fragments. Finally, only defects can be detected for which a correspondingly defective probe-DNA strand was included in the microarray in order to establish nevertheless stable duplexes. Due to these drawbacks, unknown mutations are frequently identified by denaturation based approaches. Widespread methods are real-time PCR (polymerase chain reaction) with associated melting-curve analysis and denaturing gradient gel electrophoresis DGGE. DGGE operates either with a pH-gradient or a temperature gradient along the electrophoretic path/lanes and is based on the fact that DNA duplexes with SNP defects have a lowered stability with respect to chemical or thermal denaturation. As drawbacks, real-time PCR requires fluorescent labelling and expensive instrumentation while DGGE is time consuming, severely limited towards parallelized analyses, and is an endpoint analysis without information on the kinetics of the denaturation process. To overcome these current limitations, several label-free electronic, ‘real-time’ techniques have been proposed in literature. For its analogy with chemical DGGE, we mention the impedimetric denaturation monitoring upon exposure to NaOH reported by van Grinsven et al. in the international patent application entitled “A biosensor using impedimetric real-time monitoring” and co-pending herewith. This gave clear evidence that the presence or absence of SNPs can be derived from the denaturation-time constant within a time scale of 1 to 2 minutes.
Despite of all recent progress, there still is room for an accurate denaturation based detection technique for characterising or analysing DNA/RNA based bioparticles.